1. Field of the Invention
The present invention relates to a webbing retractor device that retracts and accommodates a webbing belt for restraining a passenger seated in a seat.
2. Description of the Related Art
As disclosed, for example, in Japanese Patent Application Laid-Open (JP-A) No. 5-246303, a webbing retractor device constituting a part of a vehicle seat belt device is provided with a lock mechanism that restricts rotation of a reel shaft toward a pull-out direction at a time of rapid vehicle deceleration. A lock gear constituting a part of the lock mechanism disclosed in JP-A No. 5-246303 is able to rotate coaxially relative to the reel shaft, and when the reel shaft rotates in a pull-out direction relative to the lock gear, teeth of a main pawl and a back-up pawl respectively engage with an internal tooth formed at either side wall of a frame in conjunction with the relative rotation, restricting rotation of the reel shaft in the pull-out direction. There are two types of structure that allow the occurrence of relative rotation between the reel shaft and the lock gear, the first being a deceleration detection portion. The deceleration detection portion is provided with an inertial body that exhibits inertial movement at a time of rapid vehicle deceleration, and rotation of the lock gear is restricted by engagement of an engagement claw, which is pushed upward by the inertial movement of the inertial body, with an external tooth of the lock gear, and the lock gear rotates relative to the reel shaft, which rotates in the pull-out direction.
Further, the other structure that allows relative rotation between the reel shaft and the lock gear is an inertial body provided at the lock gear which is separate to the inertial body of the deceleration detection portion. This inertial body is connected to the lock gear by a spring, and when the lock gear rotates rapidly in the pull-out direction together with the reel shaft, the inertial body resists the biasing force of the spring due to inertia and delayed rotation occurs with respect to the lock gear. Along with relative rotation with respect to the lock gear due to the delayed rotation, the inertial body moves toward an outer side in a radial direction of the rotation of the lock gear and engages with a ratchet tooth which is an internal tooth formed at an inner side of a cover, and rotation of the inertial body and, consequently, of the lock gear, is terminated. By terminating the rotation of the lock gear in this manner, the lock gear rotates relative to the reel shaft which rotates in the pull-out direction.
However, when the lock mechanism operates inadvertently immediately after retraction of the webbing belt by the reel shaft has finished, “end-lock” occurs, whereby the reel shaft cannot rotate in the pull-out direction from this state. In a state of end-lock, it is difficult to extract of the webbing belt because the reel shaft cannot rotate in the pull-out direction. Accordingly, in the above JP-A No. 5-246303, a state of end-lock is prevented by a structure whereby the engagement claw of the deceleration detection portion and the external tooth of the lock gear do not engage when retraction of the webbing belt is complete.
However, when the spool sharply rotates slightly in the pull-out direction due to a reverse action immediately after retraction of the webbing belt is complete, there are cases when the inertial body provided at the lock gear engages with the ratchet tooth formed at the cover and when, in this state, the spool is rotated in the pull-out direction in order to extract the webbing belt, the lock mechanism operates and a state of end-lock occurs.